Rotary hydraulic machines of the subject type generally include a housing, a rotor mounted for rotation within the housing, and a plurality of vanes individually slidably disposed in corresponding radially-extending peripheral slots in the rotor. A cam ring radially surrounds the rotor, and has an inwardly directed surface forming a vane track and one or more fluid pressure cavities between the cam surface and the rotor. Inlet and outlet passages in the housing feed hydraulic fluid to and from the fluid pressure cavities.
The fluid inlet and outlet ports typically open directly into the fluid pressure cavities at the edges of the vane track. The vane outer edges are thus susceptible to chipping and damage where exposed to edges of the fluid ports. Further, in gas turbine aircraft engine pump applications, as rated pump speeds are increased, the fluid inlet port becomes smaller making inlet fuel pressure critical. It has been proposed to tailor the outside diameter of the rotor to obtain additional inlet area. However, this technique exposes the vanes to increased stress, and thus exacerbates susceptibility of the vanes to damage. Indeed, it has been found that most vane pump failures are caused by chipping or breaking of the vanes on the fluid ports or windows where the vane edges are exposed.
It is therefore a general object of the present invention to provide a rotary hydraulic machine of the subject type that eliminates porting of inlet and outlet fluid directly to the fluid pressure cavities, and thereby eliminates this cause of potential vane damage and machine failure. Yet another object of the present invention is to provide a machine of the described type, having particular utility in gas turbine aircraft engine fuel pump applications, that exhibits enhanced fluid inlet characteristics as compared with corresponding machines of similar type in the prior art. In addressing the foregoing objective, it is yet another and more specific object of the invention to provide a rotary hydraulic machine of the subject type in which fuel inlet passages are constructed to cooperate with rotation of the rotor for boosting inlet flow and pressure.